The haemodynamics of the human placenta in utero.

We have used magnetic resonance imaging (MRI) to provide important new insights into the function of the human placenta in utero. We have measured slow net flow and high net oxygenation in the placenta in vivo, which are consistent with efficient delivery of oxygen from mother to fetus. Our experimental evidence substantiates previous hypotheses on the effects of spiral artery remodelling in utero and also indicates rapid venous drainage from the placenta, which is important because this outflow has been largely neglected in the past. Furthermore, beyond Braxton Hicks contractions, which involve the entire uterus, we have identified a new physiological phenomenon, the 'utero-placental pump', by which the placenta and underlying uterine wall contract independently of the rest of the uterus, expelling maternal blood from the intervillous space.

Routine ultrasound for fetal assessment before 24 weeks' gestation.

BACKGROUND: Ultrasound examination of pregnancy before 24 weeks gestation may lead to more accurate dating and earlier diagnosis of pathology, but may also give false reassurance. It can be used to monitor development or diagnose conditions of an unborn baby. This review compares the effect of routine or universal, ultrasound examination, performed before 24 completed weeks' gestation, with selective or no ultrasound examination.  OBJECTIVES: To assess the effect of routine pregnancy ultrasound before 24 weeks as part of a screening programme, compared to selective ultrasound or no ultrasound, on the early diagnosis of abnormal pregnancy location, termination for fetal congenital abnormality, multiple pregnancy, maternal outcomes and later fetal compromise. To assess the effect of first trimester (before 14 weeks) and second trimester (14 to 24 weeks) ultrasound, separately. SEARCH METHODS: We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, and the World Health Organization's International Clinical Trials Registry Platform (ICTRP) on 11 August 2020. We also examined the reference lists of retrieved studies. SELECTION CRITERIA: We included randomised controlled trials (RCTs), quasi-RCTs, cluster-RCTs and RCTs published in abstract form. We included all trials with pregnant women who had routine or revealed ultrasound versus selective ultrasound, no ultrasound, or concealed ultrasound, before 24 weeks' gestation. All eligible studies were screened for scientific integrity and trustworthiness. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed trials for eligibility and risk of bias, extracted data and checked extracted data for accuracy. Two review authors independently used the GRADE approach to assess the certainty of evidence for each outcome MAIN RESULTS: Our review included data from 13 RCTs including 85,265 women. The review included four comparisons. Four trials were assessed to be at low risk of bias for both sequence generation and allocation concealment and two as high risk. The nature of the intervention made it impossible to blind women and staff providing care to treatment allocation.  Sample attrition was low in the majority of trials and outcome data were available for most women. Many trials were conducted before it was customary for trials to be registered and protocols published. First trimester routine versus selective ultrasound: four studies, 1791 women, from Australia, Canada, the United Kingdom (UK) and the United States (US). First trimester scans probably reduce short-term maternal anxiety about pregnancy (risk ratio (RR) 0.80, 95% confidence interval (CI) 0.65 to 0.99; moderate-certainty evidence). We do not have information on whether the reduction was sustained.  The evidence is very uncertain about the effect of first trimester scans on perinatal loss (RR 0.97, 95% CI 0.55 to 1.73; 648 participants; one study; low-certainty evidence) or induction of labour for post-maturity (RR 0.83, 95% CI 0.50 to 1.37; 1474 participants; three studies; low-certainty evidence). The effect of routine first trimester ultrasound on birth before 34 weeks or termination of pregnancy for fetal abnormality was not reported. Second trimester routine versus selective ultrasound: seven studies, 36,053 women, from Finland, Norway, South Africa, Sweden and the US. Second trimester scans probably make little difference to perinatal loss (RR 0.98, 95% CI 0.81 to 1.20; 17,918 participants, three studies; moderate-certainty evidence) or intrauterine fetal death (RR 0.97, 95% CI 0.66 to 1.42; 29,584 participants, three studies; low-certainty evidence). Second trimester scans may reduce induction of labour for post-maturity (RR 0.48, 95% CI 0.31 to 0.73; 24,174 participants, six studies; low-certainty evidence), presumably by more accurate dating. Routine second trimester ultrasound may improve detection of multiple pregnancy (RR 0.05, 95% CI 0.02 to 0.16; 274 participants, five studies; low-certainty evidence). Routine second trimester ultrasound may increase detection of major fetal abnormality before 24 weeks (RR 3.45, 95% CI 1.67 to 7.12; 387 participants, two studies; low-certainty evidence) and probably increases the number of women terminating pregnancy for major anomaly (RR 2.36, 95% CI 1.13 to 4.93; 26,893 participants, four studies; moderate-certainty evidence). Long-term follow-up of children exposed to scans before birth did not indicate harm to children's physical or intellectual development (RR 0.77, 95% CI 0.44 to 1.34; 603 participants, one study; low-certainty evidence). The effect of routine second trimester ultrasound on birth before 34 weeks or maternal anxiety was not reported. Standard care plus two ultrasounds and referral for complications versus standard care: one cluster-RCT, 47,431 women, from Democratic Republic of Congo, Guatemala, Kenya, Pakistan and Zambia. This trial included a co-intervention, training of healthcare workers and referral for complications and was, therefore, assessed separately. Standard pregnancy care plus two scans, and training and referral for complications, versus standard care probably makes little difference to whether women with complications give birth in a risk appropriate setting with facilities for caesarean section (RR 1.03, 95% CI 0.89 to 1.19; 11,680 participants; moderate-certainty evidence).  The intervention also probably makes little to no difference to low birthweight (< 2500 g) (RR 1.01, 95% CI 0.90 to 1.13; 47,312 participants; moderate-certainty evidence). The evidence is very uncertain about whether the community intervention (including ultrasound) makes any difference to maternal mortality (RR 0.92, 95% CI 0.55 to 1.55; 46,768 participants; low-certainty evidence). Revealed ultrasound results (communicated to both patient and doctor) versus concealed ultrasound results (blinded to both patient and doctor at any time before 24 weeks): one study, 1095 women, from the UK. The evidence was very uncertain for all results relating to revealed versus concealed ultrasound scan (very low-certainty evidence). AUTHORS' CONCLUSIONS: Early scans probably reduce short term maternal anxiety.  Later scans may reduce labour induction for post-maturity. They may improve detection of major fetal abnormalities and increase the number of women who choose termination of pregnancy for this reason. They may also reduce the number of undetected twin pregnancies. All these findings accord with observational data.  Neither type of scan appears to alter other important maternal or fetal outcomes, but our review may underestimate the effect in modern practice because trials were mostly  from relatively early in the development of the technology, and many control participants also had scans. The trials were also underpowered to show an effect on other important maternal or fetal outcomes.

Maternal position in the second stage of labour for women with epidural anaesthesia.

BACKGROUND: Epidural analgesia in labour prolongs the second stage and increases instrumental delivery. It has been suggested that a more upright maternal position during all or part of the second stage may counteract these adverse effects. This is an update of a Cochrane Review published in 2017. OBJECTIVES: To assess the effects of different birthing positions (upright or recumbent) during the second stage of labour, on maternal and fetal outcomes for women with epidural analgesia. SEARCH METHODS: We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (5 June 2018), and the reference lists of retrieved studies. SELECTION CRITERIA: All randomised or quasi-randomised trials including pregnant women (primigravidae or multigravidae) in the second stage of induced or spontaneous labour receiving epidural analgesia of any kind. Cluster-randomised controlled trials would have been eligible for inclusion but we found none. Studies published in abstract form only were also eligible.We assumed the experimental intervention to be maternal use of any upright position during the second stage of labour, compared with the control condition of remaining in any recumbent position. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed trials for inclusion, assessed risks of bias, and extracted data. We contacted study authors to obtain missing data. We assessed the quality of the evidence using the GRADE approach.We carried out a planned sensitivity analysis of the three studies with low risks of bias for allocation concealment and incomplete outcome data reporting, and further excluded one study with a co-intervention (this was not prespecified). MAIN RESULTS: We include eight randomised controlled trials, involving 4464 women, comparing upright positions versus recumbent positions in this update. Five were conducted in the UK, one in France and two in Spain.The largest UK trial accounted for three-quarters of all review participants, and we judged it to have low risk of bias. We assessed two other trials as being at low risk of selection and attrition bias. We rated four studies at unclear or high risk of bias for both selection and attrition bias and one study as high risk of bias due to a co-intervention. The trials varied in their comparators, with five studies comparing different positions (upright and recumbent), two comparing ambulation with (recumbent) non-ambulation, and one study comparing postural changes guided by a physiotherapist to a recumbent position.Overall, there may be little or no difference between upright and recumbent positions for our combined primary outcome of operative birth (caesarean or instrumental vaginal): average risk ratio (RR) 0.86, 95% confidence interval (CI) 0.70 to 1.07; 8 trials, 4316 women; I2 = 78%; low-quality evidence. It is uncertain whether the upright position has any impact on caesarean section (RR 0.94, 95% CI 0.61 to 1.46; 8 trials, 4316 women; I2 = 47%; very low-quality evidence), instrumental vaginal birth (RR 0.90, 95% CI 0.72 to 1.12; 8 trials, 4316 women; I2 = 69%) and the duration of the second stage of labour (mean difference (MD) 6.00 minutes, 95% CI -37.46 to 49.46; 3 trials, 456 women; I2 = 96%), because we rated the quality of the evidence as very low for these outcomes. Maternal position in the second stage of labour probably makes little or no difference to postpartum haemorrhage (PPH), (PPH requiring blood transfusion): RR 1.20, 95% CI 0.83 to 1.72; 1 trial, 3093 women; moderate-quality evidence. Maternal satisfaction with the overall childbirth experience was slightly lower in the upright group: RR 0.95, 95% CI 0.92 to 0.99; 1 trial, 2373 women. Fewer babies were born with low cord pH in the upright group: RR 0.43, 95% CI 0.20 to 0.90; 2 trials, 3159 infants; moderate-quality evidence.The results were less clear for other maternal or fetal outcomes, including trauma to the birth canal requiring suturing (average RR 1.00, 95% CI 0.89 to 1.13; 3 trials, 3266 women; I2 = 46%; low-quality evidence), abnormal fetal heart patterns requiring intervention (RR 1.69, 95% CI 0.32 to 8.84; 1 trial, 107 women; very low-quality evidence), or admission to neonatal intensive care unit (RR 0.54, 95% CI 0.02 to 12.73; 1 trial, 66 infants; very low-quality evidence). However, the CIs around some of these estimates were wide, and we cannot rule out clinically important effects.In our sensitivity analysis of studies at low risk of bias, upright positions increase the chance of women having an operative birth: RR 1.11, 95% CI 1.03 to 1.20; 3 trials, 3609 women; high-quality evidence. In absolute terms, this equates to 63 more operative births per 1000 women (from 17 more to 115 more). This increase appears to be due to the increase in caesarean section in the upright group (RR 1.29; 95% CI 1.05 to 1.57; 3 trials, 3609 women; high-quality evidence), which equates to 25 more caesarean sections per 1000 women (from 4 more to 49 more). In the sensitivity analysis there was no clear impact on instrumental vaginal births: RR 1.08, 95% CI 0.91 to 1.30; 3 trials, 3609 women; low-quality evidence. AUTHORS' CONCLUSIONS: There may be little or no difference in operative birth between women who adopt recumbent or supine positions during the second stage of labour with an epidural analgesia. However, the studies are heterogeneous, probably related to differing study designs and interventions, differing adherence to the allocated intervention and possible selection and attrition bias. Sensitivity analysis of studies at low risk of bias indicated that recumbent positions may reduce the need for operative birth and caesarean section, without increasing instrumental delivery. Mothers may be more satisfied with their experience of childbirth by adopting a recumbent position. The studies in this review looked at left or right lateral and semi-recumbent positions. Recumbent positions such as flat on the back or lithotomy are not generally used due to the possibility of aorto-caval compression, although we acknowledge that these recumbent positions were not the focus of trials included in this review.

Feasibility of a RCT of techniques for managing an impacted fetal head during emergency caesarean section: the MIDAS scoping study.

Background: Second-stage caesarean sections, of which there are around 34,000 per year in the UK, have greater maternal and perinatal morbidity than those in the first stage. The fetal head is often deeply impacted in the maternal pelvis, and extraction can be difficult. Numerous techniques are reported, but the superiority of one over another is contentious and there is no national guidance. Objective: To determine the feasibility of a randomised trial of different techniques for managing an impacted fetal head during emergency caesarean. Design: A scoping study with five work packages: (1) national surveys to determine current practice and acceptability of research in this area, and a qualitative study to determine acceptability to women who have experienced a second-stage caesarean; (2) a national prospective observational study to determine incidence and rate of complications; (3) a Delphi survey and consensus meeting on choice of techniques and outcomes for a trial; (4) the design of a trial; and (5) a national survey and qualitative study to determine acceptability of the proposed trial. Setting: Secondary care. Participants: Health-care professionals, pregnant women, women who have had a second-stage caesarean, and parents. Results: Most (244/279, 87%) health-care professionals believe that a trial in this area would help guide their practice, and 90% (252/279) would be willing to participate in such a trial. Thirty-eight per cent (98/259) of parents reported that they would take part. Women varied in which technique they thought was most acceptable. Our observational study found that impacted head is common (occurring in 16% of second-stage caesareans) and leads to both maternal (41%) and neonatal (3.5%) complications. It is most often treated by an assistant pushing the head up vaginally. We designed a randomised clinical trial comparing the fetal pillow with the vaginal push technique. The vast majority of health-care professionals, 83% of midwives and 88% of obstetricians, would be willing to participate in the trial proposed, and 37% of parents reported that they would take part. Our qualitative study found that most participants thought the trial would be feasible and acceptable. Limitations: Our survey is subject to the limitation that, although responses refer to contemporaneous real cases, they are self-reported by the surgeon and collected after the event. Willingness to participate in a hypothetical trial may not translate into recruitment to a real trial. Conclusions: We proposed a trial to compare a new device, the fetal pillow, with a long-established procedure, the vaginal push technique. Such a trial would be widely supported by health-care professionals. We recommend that it be powered to test an effect on important short term maternal and baby outcomes which would require 754 participants per group. Despite the well-known difference between intent and action, this would be feasible within the UK. Future work: We recommend a randomised controlled trial of two techniques for managing an impacted fetal head with an in-built internal pilot phase and alongside economic and qualitative substudies. Study registration: This study is registered as Research Registry 4942. Funding: This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 27, No. 6. See the NIHR Journals Library website for further project information.

Text: One-quarter of UK pregnant women have a caesarean section. Most of these procedures are straightforward, but in a small number of cases unexpected complications can make the birth difficult. One complication, an impacted fetal head, may happen when caesarean sections are done in the second 'pushing' stage of labour. If the baby's head is low and wedged in the woman's pelvis, lifting it can be difficult, which can result in damage to the mother's womb and vagina, and to her baby. Occasionally, babies die. There are different techniques doctors and midwives can use to make these births easier, but there is uncertainty around which is best. To plan a trial to test these techniques, we needed to know how often impacted head happens, what techniques are used to manage it and whether or not research is acceptable to parents and health-care professionals. We surveyed doctors and midwives to find out which techniques they use and what training they need. We surveyed parents and pregnant women and interviewed women who had experienced a second-stage caesarean. We collected information from UK hospitals to find out how common this is and the impact on women and babies. We found out the following. List: • Around 7% of caesareans take place in second stage, and impacted fetal head occurs in 16% of these births. List: • One-third of women would consent to take part in a trial, if the complication happened to them. List: • Nearly all midwives and doctors thought that this research was important and would be willing to take part. Text: Using all of the information we collected, we designed a clinical trial. We wanted to compare two techniques for managing an impacted fetal head. The first is the vaginal push technique, where the doctor or midwife puts their hand into the mother's vagina to push her baby's head up, and the second is the fetal pillow, a device inserted into the mother's vagina before the operation starts to dislodge the baby's head upwards.

The test accuracy of antenatal ultrasound definitions of fetal macrosomia to predict birth injury: A systematic review.

OBJECTIVES: To determine which ultrasound measurement for predicted fetal macrosomia most accurately predicts adverse delivery and neonatal outcomes. STUDY DESIGN: Four biomedical databases searched for studies published after 1966. Randomised trials or observational studies of women with singleton pregnancies, resulting in a term birth who have undergone an index test of interest measured and recorded as predicted fetal macrosomia ≥28 weeks. Adverse outcomes of interest included shoulder dystocia, brachial plexus injury (BPI) and Caesarean section. RESULTS: Twenty-five observational studies (13,285 participants) were included. For BPI, the only significant positive association was found for Abdominal Circumference (AC) to Head Circumference (HC) difference > 50 mm (OR 7.2, 95 % CI 1.8-29). Shoulder dystocia was significantly associated with abdominal diameter (AD) minus biparietal diameter (BPD) ≥ 2.6 cm (OR 4.2, 95 % CI 2.3-7.5, PPV 11 %) and AC > 90th centile (OR 2.3, 95 % CI 1.3-4.0, PPV 8.6 %) and an estimated fetal weight (EFW) > 4000 g (OR 2.1 95 %CI 1.0-4.1, PPV 7.2 %). CONCLUSIONS: Estimated fetal weight is the most widely used ultrasound marker to predict fetal macrosomia in the UK. This study suggests other markers have a higher positive predictive value for adverse outcomes associated with fetal macrosomia.

Maternal smoking during pregnancy and fetal organ growth: a magnetic resonance imaging study.

OBJECTIVE: To study whether maternal cigarette smoking during pregnancy is associated with alterations in the growth of fetal lungs, kidneys, liver, brain, and placenta. DESIGN: A case-control study, with operators performing the image analysis blinded. SETTING: Study performed on a research-dedicated magnetic resonance imaging (MRI) scanner (1.5 T) with participants recruited from a large teaching hospital in the United Kingdom. PARTICIPANTS: A total of 26 pregnant women (13 current smokers, 13 non smokers) were recruited; 18 women (10 current smokers, 8 nonsmokers) returned for the second scan later in their pregnancy. METHODS: Each fetus was scanned with MRI at 22-27 weeks and 33-38 weeks gestational age (GA). MAIN OUTCOME MEASURES: Images obtained with MRI were used to measure volumes of the fetal brain, kidneys, lungs, liver and overall fetal size, as well as placental volumes. RESULTS: Exposed fetuses showed lower brain volumes, kidney volumes, and total fetal volumes, with this effect being greater at visit 2 than at visit 1 for brain and kidney volumes, and greater at visit 1 than at visit 2 for total fetal volume. Exposed fetuses also demonstrated lower lung volume and placental volume, and this effect was similar at both visits. No difference was found between the exposed and nonexposed fetuses with regards to liver volume. CONCLUSION: Magnetic resonance imaging has been used to show that maternal smoking is associated with reduced growth of fetal brain, lung and kidney; this effect persists even when the volumes are corrected for maternal education, gestational age, and fetal sex. As expected, the fetuses exposed to maternal smoking are smaller in size. Similarly, placental volumes are smaller in smoking versus nonsmoking pregnant women.

Would gestational age and presence of brain anomalies affect interobserver reliability of fetal head biometry? Using off-line analysis of 3-D dataset.

The objective was to assess interobserver reliability of fetal head biometry using archived three-dimensional (3-D) volumes and the impact of gestational age and presence of brain anomalies on examiners' performance. Seventy nine 3-D volume datasets of fetal head were examined: 27 were normal and 52 had brain abnormalities. Off-line analysis was done by three fetal medicine experts (E1, E2 and E2), all were blinded to history and patient details. Measurements of the biparietal diameter (BPD), head circumference (HC), lateral ventricle (Vp) and transcerebellar diameter (TCD) were compared between examiners and to two-dimensional (2-D) measurements. Comparisons were made at two gestational age groups (≤22 and >22 weeks) and in presence and absence of brain anomalies. The intraclass coefficient showed a significantly high level of measurement agreement between 3-D examiners and 2-D, with values >0.9 throughout (p < 0.001). Bias was evident between 3-D examiners. E2 produced smaller measurements. The mean percentage difference between this examiner and the other two in BPD, HC, Vp and TCD measurements was significant, of 1.6%, 1%, 4.9% and 1.8%, respectively. E1 measured statistically larger for HC and TCD. E3 measured significantly larger for only BPD. The presence of anomalies was of no influence on the 3-D examiners' performance except for E3 who showed bias in BPD measurements only in cases with brain anomalies. Unlike other examiners, bias of E2 was only seen at gestational age group ≤22 weeks. Limits of agreement in measurements between observers were narrow for all parameters but were widest for the Vp measurements, being ±23% of the mean difference. Despite the above bias, the actual mean difference between examiners was small and unlikely to be of any clinical significance. Off-line measurement of fetal head biometry using 3-D volumes is reliable. In our study, presence of brain anomalies was unlikely to influence the reproducibility of measurements. Gestational age seemed to be of an impact on examiners' bias. Among experts this bias may be of no clinical significance.

Evaluating the intra- and interobserver reliability of three-dimensional ultrasound and power Doppler angiography (3D-PDA) for assessment of placental volume and vascularity in the second trimester of pregnancy.

Three-dimensional (3-D) power Doppler angiography (3-D-PDA) allows visualisation of Doppler signals within the placenta and their quantification is possible by the generation of vascular indices by the 4-D View software programme. This study aimed to investigate intra- and interobserver reproducibility of 3-D-PDA analysis of stored datasets at varying gestations with the ultimate goal being to develop a tool for predicting placental dysfunction. Women with an uncomplicated, viable singleton pregnancy were scanned at 12, 16 or 20 weeks gestational age groups. 3-D-PDA datasets acquired of the whole placenta were analysed using the VOCAL software processing tool. Each volume was analysed by three observers twice in the A plane. Intra- and interobserver reliability was assessed by intraclass correlation coefficients (ICCs) and Bland Altman plots. At each gestational age group, 20 low risk women were scanned resulting in 60 datasets in total. The ICC demonstrated a high level of measurement reliability at each gestation with intraobserver values >0.90 and interobserver values of >0.6 for the vascular indices. Bland Altman plots also showed high levels of agreement. Systematic bias was seen at 20 weeks in the vascular indices obtained by different observers. This study demonstrates that 3-D-PDA data can be measured reliably by different observers from stored datasets up to 18 weeks gestation. Measurements become less reliable as gestation advances with bias between observers evident at 20 weeks.

A novel technique for the semi-automated measurement of embryo volume: an intraobserver reliability study.

The aim was to assess intraobserver reliability of a new semi-automated technique of embryo volumetry. Power calculations suggested 46 subjects with viable, singleton pregnancies were required for reliability analysis. Crown rump length (CRL) of each embryo was analyzed using 2-D and a 3-D dataset acquired using transvaginal ultrasound. Virtual organ computer-aided analysis (VOCAL) was used to calculate volume of gestation sac (GSV) and yolk sac (YSV) and SonoAVC (sonography-based automated volume count) was used to quantify fluid volume (FV). Embryo volume was calculated by subtracting FV and YSV from GSV. Each dataset was measured twice. Reliability was assessed using Bland-Altman plots and intraclass correlation coefficients (ICCs). Fifty-two datasets were analyzed. Median embryo volume was 1.8 cm(3) (0.1 to 8.1 cm(3)); median gestational age 7 + 4 weeks; median CRL 13 mm (2 to 29 mm). Mean difference of embryo volume measurements was 0.1cm(3) (limits of agreement [LOA] -0.3 to 0.4 cm(3)); multiples of mean (MoM) 0.38; mean difference of CRL measurements 0.3 mm (LOA -1.4 to 2.0 mm), MoM = 0.26. ICC for embryo volume was 0.999 (95%CI 0.998 to 0.999), confirming excellent intraobserver agreement. ICC for CRL was 0.996 (95%CI 0.991 to 0.998). Regression analysis showed good correlation between embryo volume and CRL (R(2) = 0.60). The new semi-automated 3-D technique provides reliable measures of embryo volume. Further work is required to assess the validity of this technique.